SPATIALLY-RESOLVED MEASUREMENTS OF SOOT VOLUME FRACTION USING LASER-INDUCED INCANDESCENCE

Laser-induced incandescence is used to obtain spatially resolved measu rements of soot volume fraction in a laminar diffusion flame, in which comparisons with laser scattering/extinction data yield excellent agr eement. In addition, the laser-induced incandescence signal is observe d to involve a rapid rise in intensity followed by a relatively long ( ca. 600 ns) decay period subsequent to the laser pulse, while the effe ct of laser fluence is manifest in nonlinear and near-saturated respon se of the laser-induced incandescence signal with the transition occur ring at a laser fluence of approximately 1.2 X 10(8) W/cm2. Spectral r esponse of the laser-induced incandescence involves a continuous spect rum in the visible wavelength range due to the blackbody nature of the emission. Simultaneous measurements of laser-induced incandescence an d light scattering yield encouraging results concerning the mean soot particle diameter and number concentration. Thus, laser-induced incand escence can be used as an instantaneous, spatially resolved diagnostic of soot volume fraction without the need for the conventional line-of -sight laser extinction method, while potential applications in two-di mensional imaging and simultaneous measurements of laser-induced incan descence and light-scattering to generate a complete soot property cha racterization are significant.